1. Field of the Technology
The present application relates generally to data communication for wireless communication devices, and more particularly to methods and apparatus for re-establishing communication for a wireless communication device after a communication loss in a wireless communication network.
2. Description of the Related Art
Wireless communication devices, when operating within poor coverage areas of a wireless communication network such as a wireless packet-switched network, may only be able to send and receive traffic during sporadic intervals. This causes conventional notions of packet-switched data transactions to break down. Conventional approaches, such as simply retrying transmissions using a back-off algorithm, will result in either an intensive use of radio resources or poor reliability, especially for communication in a direction from the network to the wireless device.
Many known wireless networks exploit the notion of a wireless device querying data from a server, as typically employed in most Internet transactions. This includes, for example, requests for web pages and periodic polling of an e-mail server for new e-mail by an e-mail program. In this conventional “pull” approach, the typical traffic pattern is the wireless device sending to the network followed by the network sending a response to the wireless device. When the network is sending to the wireless device, it is always doing so a short time after the quality of the link has been established. If the transaction fails due to poor coverage, the wireless device or user may wait for coverage to improve and subsequently retry the query. However, the onus is on the wireless device to retry the transaction after any such communication problems.
An alternate communication scheme uses a “push” methodology. “Push” refers to data being pushed to the wireless device from the network. The conventional Internet notion of periodic polling for new data (such as e-mail messages) is undesirable as it is thought to be too radio resource intensive for a wireless device application. As an alternative, push requires that an exchange of traffic be initiated from the network side. Many packet-switched wireless networks have provisions for network-initiated traffic.
In one known push approach, the network will attempt to contact a wireless device several times either by sending a packet directly or paging the wireless device. This approach works well for a small number of retries, but if a large number of devices have pending traffic, the network's ability to contact devices may be quickly exhausted without exchanging any useful traffic. To limit wasting radio resources attempting to contact wireless devices, a typical network will only attempt to contact a wireless device a limited number of times and subsequently stop trying until the device makes itself known to the network again. Thus, the wireless devices may indicate to the network that they have regained coverage after a period being out of coverage. Such an indication informs the network that it may send to the wireless device again, even if the network has previously stopped trying to contact the wireless device. A fundamental problem with this approach is that the wireless device may not know whether its coverage is in fact adequate without testing the network's ability to receive communication signals transmitted by the wireless device. However, testing how well the network receives communication signals from the wireless device can only reliably be determined by actually sending packets to the network. This uses radio resources and is thus not done very often.
Some networks, such as General Packet Radio Service (GPRS) based networks, force a wireless device to periodically indicate to the network that it is in fact available on the network. Again, however, this uses radio resources and is therefore performed at relatively long intervals, typically on the order of an hour. While this periodic transmission will get the network and wireless device's view of coverage in sync, the network's view of coverage may be very different from the wireless device's view between these periodic transmissions to the network.
Further issues arise in connection with the use of one or more application servers (e.g. an e-mail server) which provide voice and/or data services to the wireless devices. For one, an application server will lose its connection with a wireless device after a communication loss between the wireless device and the wireless network (e.g. out of coverage situation). If the data connection is not automatically re-established once the wireless device regains adequate signal coverage, the wireless device may not adequately receive continued service(s) from the application server. If the application server is configured to automatically re-establish the connection with the wireless device once broken, however, it may undesirably flood the network with connection requests to the wireless device while it is still unavailable.
Accordingly, there is a resulting need for improved methods and apparatus for re-establishing communication for a wireless communication device after a communication loss in a wireless communication network.